[xen staging-4.18] x86/msr: expose MSR_FAM10H_MMIO_CONF_BASE on AMD

[patchbot@xxxxxxx]

commit e6219bc97e7df4b0a82f35f9b9bf0a3aed96e8d5
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Thu Mar 20 13:33:12 2025 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 20 13:33:12 2025 +0100

    x86/msr: expose MSR_FAM10H_MMIO_CONF_BASE on AMD
    
    The MMIO_CONF_BASE reports the base of the MCFG range on AMD systems.
    Linux pre-6.14 is unconditionally attempting to read the MSR without a
    safe MSR accessor, and since Xen doesn't allow access to it Linux reports
    the following error:
    
    unchecked MSR access error: RDMSR from 0xc0010058 at rIP: 
0xffffffff8101d19f (xen_do_read_msr+0x7f/0xa0)
    Call Trace:
     xen_read_msr+0x1e/0x30
     amd_get_mmconfig_range+0x2b/0x80
     quirk_amd_mmconfig_area+0x28/0x100
     pnp_fixup_device+0x39/0x50
     __pnp_add_device+0xf/0x150
     pnp_add_device+0x3d/0x100
     pnpacpi_add_device_handler+0x1f9/0x280
     acpi_ns_get_device_callback+0x104/0x1c0
     acpi_ns_walk_namespace+0x1d0/0x260
     acpi_get_devices+0x8a/0xb0
     pnpacpi_init+0x50/0x80
     do_one_initcall+0x46/0x2e0
     kernel_init_freeable+0x1da/0x2f0
     kernel_init+0x16/0x1b0
     ret_from_fork+0x30/0x50
     ret_from_fork_asm+0x1b/0x30
    
    Such access is conditional to the presence of a device with PnP ID
    "PNP0c01", which triggers the execution of the quirk_amd_mmconfig_area()
    function.  Note that prior to commit 3fac3734c43a MSR accesses when running
    as a PV guest would always use the safe variant, and thus silently handle
    the #GP.
    
    Fix by allowing access to the MSR on AMD systems for the hardware domain.
    
    Write attempts to the MSR will still result in #GP for all domain types.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: b4071d28c5bd9ca4fed76031cbf0e782b74209b9
    master date: 2025-03-12 13:32:30 +0100
---
 xen/arch/x86/msr.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index 9babd441f9..16eac6ae60 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -243,6 +243,14 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t 
*val)
         *val = 0;
         break;
 
+    case MSR_FAM10H_MMIO_CONF_BASE:
+        if ( !is_hardware_domain(d) ||
+             !(cp->x86_vendor & (X86_VENDOR_AMD | X86_VENDOR_HYGON)) ||
+             rdmsr_safe(msr, *val) )
+            goto gp_fault;
+
+        break;
+
     case MSR_VIRT_SPEC_CTRL:
         if ( !cp->extd.virt_ssbd )
             goto gp_fault;
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.18